Another plot could involve time - travel gone wrong. Marinette tries to go back in time to fix a major mistake, but something disrupts the time - space continuum and she gets caught in a loop that ultimately leads to her death.
One possible plot could be that they finally confess their long - hidden feelings for each other after a series of misunderstandings and adventures. They end up in a moment of intimacy in bed and share a kiss. Another could be a situation where they are in a fake relationship at first for some external reason, but as they spend more time together in the same living space, feelings develop and lead to the kiss in bed. Or perhaps they are in a dangerous situation, like being trapped somewhere, and the closeness and shared vulnerability lead to the romantic moment.
One possible plot could be Percy sacrificing himself to save his friends while in Poseidon's arms. Maybe there's a great battle against an unbeatable foe, and Percy realizes the only way to victory is through his own death. He accepts his fate in Poseidon's comforting embrace.
One possible plot could be that Naruto sacrifices himself to save the village from a powerful and ancient evil. He uses all his chakra in a last - ditch effort to seal away the threat forever, leaving the village in mourning but also in a state of safety. Another plot might involve Naruto being poisoned by an enemy who has infiltrated the village. Despite the efforts of Sakura and the others, they can't find a cure in time, and Naruto succumbs to the poison. A third idea could be that in a battle against a new, incredibly strong foe, Naruto is overpowered and killed, which then spurs the rest of the shinobi world to come together to avenge his death.
One possible plot could be how the Occult Research Club copes with Issei's death. They might struggle to move forward while also trying to figure out who was behind his death. Maybe they suspect a powerful enemy from the Underworld or a rogue devil. Another idea could be that Issei's death sets off a chain of events that leads to a new power struggle in the supernatural world, as different factions vie for the power he once held or the influence he had over certain areas. And his friends could be visited by his spirit in dreams, guiding them to uncover secrets he didn't have time to reveal before his death.
A possible plot could be that the dragon is a new, unknown and extremely powerful species. Harry is sent to investigate it but underestimates its power and gets killed.
One interesting plot could be Marinette being akumatized into a form that has the power to reverse the roles of heroes and villains in Paris. So, the akuma victims become the ones trying to save Ladybug and Chat Noir. Another plot might involve her akumatized form having the ability to create illusions of everyone's worst fears, which leads to chaos in the city as people are forced to face their phobias.
Perhaps in the 'naruto dies narusaku fanfic', Naruto sacrifices himself to save Sakura from a powerful enemy. Sakura, in her despair, starts to discover new aspects of Naruto she never fully realized when he was alive. She could then start a journey to find a way to bring him back, encountering many challenges along the way and meeting old friends and foes who either help or hinder her.
Maybe in the fanfic, Aunt May's death is the catalyst for Peter to take on a more serious and darker approach to fighting crime. He could start to question his no - killing rule more severely. For example, he might face a villain who was directly or indirectly responsible for Aunt May's death and be on the verge of crossing that line.
One possible plot could be that Ruby is facing an overwhelmingly powerful enemy alone. Despite her best efforts, she is mortally wounded in the battle and dies heroically. Another could be that she sacrifices herself to save her friends from a deadly trap or a powerful Grimm attack.
One possible plot could be about how her friends deal with the grief. They might gather to remember the good times they had with her, sharing stories and mementos.